Mimosa bush/briar bush/yellow mimosa – Vachellia farnesiana (previously Acacia farnesiana).

An invasive and thorny plant taking over grazing properties in north-western New South Wales and beyond. It is now well established over large areas around Moree, Pallamallawa, Boggabilla and Yetman. It continues to spread into new areas. (YouTube 2006 Mimosa Bush Awareness video 30 sec)

NWW78027 Mimosa bush near Yetman NSW

NWW78027 Mimosa bush near Yetman NSW

This plant is very difficult, and costly, to control (see details of herbicide trials, below). Mimosa bush is NOT a declared noxious weed in New South Wales. It is, in fact, classed as a native plant (despite its supposed origin). Flora of New South Wales states that mimosa bush is: “Native of trop. Amer., probably introduced into Aust. prior to European settlement. Widely cultivated overseas for its decorative qualities and the essential oil obtained from its flowers for use in the perfume industries. It is grown for hedges and windbreaks, however, it may form dense thickets and become weedy.”

Since August 2013, mimosa bush has been declared as a “feral native”, thereby removing major restrictions on its control (Copy of media release).

Mimosa bush - very invasive plant - NWW7806

Mimosa bush – very invasive plant – NWW7806

Mimosa bush has some uses: it is regarded by some as a useful source of food for sheep. Sheep (and goats, camels) tend to keep the plant under control, but over the past 20 years or more changes in land management, reduced sheep numbers and the move into cattle has seen the plant really “take off”. Cattle also find food value in the plant – especially the seed pods. And, the viable seeds pass unscathed through the stomach and are therefore a major contributor to the ever-increasing number of new plants every year.

Photo (above left) shows close-up of mimosa bush. Note the thorns, and the bean-like seed pods. Each seed pod contains about 10 seeds. The pods are a good food source, rich in protein. Cattle feed on the mimosa bush pods. The seeds pass through the animals and are subsequently

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Mimosa bush seed pod – usually around 10 seeds per pod…

dropped at random anywhere in the paddock. Photo (left) shows close-up of seed pods.

EFFECT ON ANIMALS

Mimosa bush has useful qualities as a food source at different times of the year. However, it is a very invasive and drought-resistant plant and if left unchecked severely reduces a property’s stock-carrying capacity. As time progresses, the plants can effectively take over the whole paddock! Mustering of livestock becomes very difficult – if not impossible – in areas like these. And of course, wonderful for the wild pig population!

IDENTIFICATION

Mimosa bush usually grows to a height of around 1 to 1.5 metres. Almost every part of the plant contains sharp thorns. Flowers are similar to some species of wattle: fluffy and yellow. The seed pods are a prominent feature of the plant. Stock seek out and eat the pods, spreading the seeds as they move on around the paddock.

MORE INFORMATION:

Plants of Western New South Wales, by Cunningham, Mulham, Milthorpe & Leigh (published by Inkata Press).

CONTROL METHODS –

Non-Chemical Options: Manual control, in the form of pushing plants out of the ground with a tractor blade or the like, is NOT RECOMMENDED unless followed up with a herbicide treatment program or, where possible, ploughing, cropping etc. While clearing gives an immediate impression that the problem has been solved, the same area will soon be infested with regrowth from broken root parts. And, dozens of small seedlings will also emerge because the parent plants have been taken out.

SLASHING is another non-chemical management option. There is an immediate result of course – the area looks good and can be accessed again by animals and vehicles – but follow-up has to be continued. SLASHING AFTER A FIRE EVENT can produce even better results.

Chemical Options: It seems there is no herbicide that will do a 100% job every time. The plant’s efficient root system is so hard to infiltrate, especially when plants get a bit of size on them (a 10m tap-root on mature plants is not uncommon). Timing is another factor – like all plants, they need to be healthy and with plenty of leaf to absorb the herbicide.

According to NSW DPI’s excellent booklet “Noxious and Environmental Weed Control Handbook Fifth Edition” (and more recent updates) treatments for Mimosa bush include:

Chemical options Rate: Spot/Boom Comments
Fluroxypry eg Starane Advanced®  1.8 L in 100 L of diesel (= 1 L in 55 L diesel)  Basal bark application – treatment of plants up to 5 cm diameter
Triclopyr + Picloram Access ® 1.0 L in 60 L of diesel Cut stump/basal bark application. (Ensure all stems are treated. Delay treatment of regrowth on bulldozed plants until regrowth 1m high).
Tebuthiuron pellets 200g/kg eg Tebulan®, Graslan® etc  2.0 g/m220 kg/ha  Follow all relevant label instructions when applying product. Estimate the area within 30 cm beyond the drip zone of each target weed or group of weeds and calculate the amount of Tebulan/Graslan to cover area to be treated. Distribute the required dose uniformly within this area. More than one application may be necessary. Preferred timing of application October to April. Results will be dependant on rainfall and subsequent movement of the herbicide into the ground. Nil withholding when used according to label/permit. Please check details as per Permit 13891 (expires 31/3/2023 – for use in Qld and NSW only.)
Clopyralid 300g/L eg Lontrel®, Clock® 300 etc 500 ml in 100 L of water plus surfactant eg BS1000® 100 mL per 100 L of water Apply as a high volume spray. Full coverage of shrub is essential. Apply to actively growing shrubs in full leaf.

Please check full details as per Permit 14929  (registered until 30/9/2019 – for use in NSW, Qld, SA only.(If using 600g/L clopyralid – eg Lontrel Advanced® – mixing rate would be halved to 250 mL in 100 L of water) 

Clopyralid 600g/L eg Lontrel®, Advanced®:  250 ml in 100 L of water plus surfactant eg BS1000® 100 mL per 100 L of water
More information on mimosa bush herbicide trials below…

IMPORTANT: USE OF PESTICIDES – ALWAYS READ THE LABEL Pesticides must only be used for the purpose for which they are registered and must not be used in any other situation or in any manner contrary to the directions on the label. Never use a herbicide in any way contrary to the label recommendations.

HERBICIDE TRIALS YETMAN COMMON 2006-2010

This trial plot is still clearly signposted adjacent to the Bruxner Highway 200m south of Yetman. [Photo #19 left taken during a subsequent trials evaluation - L to R Clem McLeod, Les Tanner, Stephen Kneller, Tony Cook, Doug Stieger

Participants in the Yetman mimosa bush trials (left to right) Clem McLeod, Les Tanner, Stephen Kneller, Tony Cook, Doug Stieger

November 2006 – North West Weeds County Council (at that time representing Inverell and Gwydir Shire Councils), in conjunction with NSW DPI, Dow Agrosciences, Dupont, Macspred and the Yetman Common Trust, commenced a new series of herbicide trials on mimosa bush. The same trials were replicated in March 2007 to compare results of application timing. See PDF copy of herbicides used.

Results:
(1) 12 months later – an assessment by Tony Cook (NSW DPI)
(2) 24 and 36 months later – assessment by Les Tanner, NW Weeds County Council

Further trials Dec 2007, Apr 2008, Apr 2010, May 2010
Inverell Shire Council continued a further trials during 2007-2010 using various rates of Lontrel®, Grazon Extra®, Graslan® pellets and other available herbicides at other sites in the Yetman Common. Some other applications method were also trialed: mulching and “wet-blade” technology.

Results:
Monitoring and assessments of these trials has all been summarised in the 2-page PDF document Mimosa bush trials Yetman Common 2007-2013 LRT.

Moving on: Gwydir Shire (with assistance from Tony Cook, DPI Tamworth) applied for two (2) APVMA general permits: one to use a mix of Grazon® and Uptake Oil® (or equivalents in other brands) and the other to use Graslan® pellets (or equivalent). The permit for the pellets is still in effect (see herbicide table above).

The trials also confirmed the effectiveness of Clopyralid (eg Lontrel®) on mimosa bush control. This mixture still appears to be the best choice for high volume treatment of mimosa bush. See listing in the herbicides schedule above.

Again, there is no guarantee that any herbicide mixture will do the complete job – especially on a plant that can put down such an effective tap root. It seems we have to accept the fact that most mature plants will require follow-up treatment, whatever we use. That is why it is so important for landholders to get in early and stop this plant before it becomes established. Small plants are not hard to kill.

A SUMMARY OF THE TRIALS – AS AT SEP 2015

  • Results to date indicate Clopyralid (eg Lontrel®, Clock® 300 etc) is still the most effective folia spray.  
  • Good results were achieved from treatments using the Wetblade® system (simultaneous slashing and
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    Wetblade demo Yetman mimosa bush trials 11 May 2010

    herbicide application, as in photos, right). However, while this system instantly converts a thick area of mimosa bush into a “golf course” [almost], its high cost limits use over large areas. A larger unit would certainly be worth investigating.

  • The Velpar® trials plot produced a surprising result. It certainly has potential for use in selected areas but at this stage Velpar® (or equivalents in other brands) is not registered for use on mimosa bush.
  • Grassland® pellets (or equivalents in other brands) are easily transported on the quad or the ute and are convenient to use especially on isolated plants. (Results from the pellets on the Yetman trial plot #17 were disappointing – the target patch was very large and very old and possibly did not receive a heavy enough dose?) Generally, good results are being achieved because this treatment is still being widely used by a number of landholders particularly in the Yetman area.
  • Starane®/ and Access® (or their equivalents in other brands) in diesel are effective for basal bark application. Very expensive per litre but each litre goes a long way – ideal for small areas and/or isolated plants. Also reasonably effective as an immediate follow-up spray on plants being pushed out with a blade…

The Yetman Mimosa Bush Field Day 2007
Approx 150 people showed up on the day – all hoping to hear that a magic solution had been found to fix the mimosa bush problem…

NWW78010WX Mimosa bush field day Yetman

NWW78010WX Mimosa bush field day Yetman

NWW78048WX-Mimosa-Bush-Field-Day-Yetman-10-Dec-2007

NWW78048WX-Mimosa-Bush-Field-Day-Yetman-10-Dec-2007

NWW78049WX Yetman MR trial site signage Mar 2007

NWW78049WX Yetman MR trial site signage Mar 2007

DISCLAIMER: The information contained in this web site is based on knowledge and understanding at the time of writing. However, because of advances in knowledge, users are reminded of the need to ensure that information upon which they rely is up to date and to check currency of the information with the appropriate officer of North West Weeds or the user’s independent adviser. Les Tanner 26/11/2015